1. Field of the Invention
The present invention relates to an exposure mask manufacturing method, an drawing apparatus, a semiconductor device manufacturing method, and a mask blanks product in a semiconductor field.
2. Description of the Related Art
As semiconductor devices become smaller, there is an increasing demand for miniaturization in a photolithography process. Already, the device design rule is as small as 65 nm. Accordingly, the pattern dimension precision is required to be controlled very strictly at 5 nm or less.
In a semiconductor manufacturing process, a multilayer pattern is formed by using plural photo masks. At this time, an alignment precision between upper and lower patterns is also very strict, same as in pattern dimension precision, in the trend of the finer design rule.
In this background, hindering factors of high precision in a pattern forming process include deformation such as distortion of photo masks occurring when the photo masks for use in the photolithography process is chucked in the exposure apparatus.
Recently, to achieve a desired flatness, a photo mask has been developed, which guarantees a desired flatness in a state that the photo mask is chucked in the exposure apparatus by predicting in advance flatness of the mask after chucking of the photo mask (Jpn. Pat. Appln. KOKAI Publication No. 2003-050458). The mask flatness is extremely excellent in a state that the photo mask is chucked in the exposure apparatus.
However, there are many cases in which precision of a mask pattern position becomes problematic. The reasons are considered as follows.
A photo mask manufacturing process includes a process of drawing a mask pattern on a mask blanks substrate by using a mask drawing apparatus. The mask drawing apparatus holds the mask blanks substrate so as not to distort the mask blanks substrate as much as possible. For example, the mask blanks substrate is held at three points. Thus, the mask pattern is drawn in a state that native flatness of the mask blanks substrate is maintained.
A wafer pattern manufacturing process includes a process of transferring a mask pattern on a wafer by using a wafer exposure apparatus. The wafer exposure apparatus chucks a photo mask by using a chucking mechanism such as a vacuum chucking mechanism. By using such a chucking mechanism, however, the photo mask is deformed.
Therefore, as shown in FIG. 18, a position of a pattern 92 is deviated by δ between the case where a photo mask 91 is not deformed (before chucking) and the case where the photo mask is deformed (after chucking). When deformed like warp as shown in FIG. 18 (warp is schematically indicated by inclined straight line) is arised, the position of the pattern 92 is deviated to right side. Meanwhile, when the photo mask in the Jpn. Pat. Appln. KOKAI Publication is used, the flatness of the photo mask after chucking is improved.
Whether the photo mask in the Jpn. Pat. Appln. KOKAI Publication is used or not, chucking the photo mask causes the deformation in the photo mask, and thus, the mask pattern cannot be correctly transferred onto the wafer precisely as the pattern position before chucking.
So far, position deviation of a mask pattern due to deformation of a photo mask was not a serious problem. However, since the pattern dimension precision is required to be very strict, 5 nm or less, at the present, such a problem cannot be ignored.